Poorly differentiated colorectal adenocarcinomas show higher rates of microsatellite instability and promoter methylation of p16 and hMLH1: a study matched for T classification and tumor location

Potential neuroendocrine differentiation in poorly differentiated colorectal adenocarcinoma: A hidden trait?

Neuroendocrine carcinoma (NEC) of the colon and rectum is a rare malignancy with a poor prognosis that is characterized by distinct clinical and histopathological features that differ significantly from those of more prevalent adenocarcinomas. Poorly differentiated colorectal adenocarcinoma (PDC) is also rare and carries a poor prognosis. Considering the morphological similarities between these two rare, poorly differentiated cancers of the colon and rectum, it is plausible that certain cases of colorectal cancer (CRC) diagnosed as PDC may contain NEC as well. In the present study, cases of CRC that were diagnosed as PDC at our institution were investigated, searching for patients who exhibited NEC characteristics based on the expression of neuroendocrine markers (NEMs), including chromogranin A, synaptophysin and insulinoma-associated 1 (INSM1), and the loss of retinoblastoma 1 (Rb). Of 816 total CRC cases, 74 cases (9.1%) were identified as PDC. These were further divided into 13 (17.5%) cases that were positive for NEMs and others. Of these 13 cases, the expression rates for chromogranin A and synaptophysin were 69.2% each, while that of INSM1 was 100%. Upon re-examination of the 13 PDC cases, two cases were morphologically identified as NEC, including one large- and one small-cell NEC. A total of two cases showed loss of Rb in their PDC lesions. NEM positivity was considered an independent prognostic factor in the 74 PDC cases. Among these cases, some may exhibit characteristics of NEC. Unraveling the molecular mechanisms using CRC that harbors both PDC and NEC will be a task for future research.

Concordance between microsatellite instability testing and immunohistochemistry for mismatch repair proteins and efficient screening of mismatch repair deficient gastric cancer

Microsatellite instability (MSI) testing, an established technique that has gained prominence in recent years for its predictive potential regarding the efficacy of immune checkpoint inhibitors, is used to evaluate DNA mismatch repair (MMR) deficiency (dMMR). As with other methods, the immunohistochemistry (IHC) of MMR proteins is also widely adopted. Although both techniques have been validated, their concordance rate remains unknown, particularly regarding non-colorectal cancer. Therefore, the aim of the present study was to explore and elucidate their concordance in the context of gastric cancer (GC). A total of 489 surgically resected primary GC tissues were analyzed to compare the results yielded by the MSI test and those from IHC. Of 488 GC cases, 56 (11.5%) exhibited a loss of MMR proteins, whereas 52 (10.7%) were classified as high-frequency MSI (MSI-H). The concordance rate between these two categories was 99.2%. The microsatellite markers BAT26 and MONO27 demonstrated 100% sensitivity and 99.5% specificity in detecting dMMR GC. In addition, histopathological analysis revealed that MSI-H was more prevalent in GCs exhibiting coexisting Tub2 and Por1 subtypes. However, four discordant cases were observed. All four cases were microsatellite-stable cases but exhibited loss of MLH1 protein expression with hypermethylation of the MLH1 promoter. The results of the present study highlight that while there is a strong concordance between MSI and IHC testing results for determining dMMR status, IHC testing may offer superior efficacy in detecting dMMR.

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

Colorectal cancer is one of the most common cancers, and diagnosis at late metastatic stages is the main cause of death related to this cancer. This progression to metastasis is complex and involves different molecules such as the chemokine CXCL12 and its two receptors CXCR4 and CXCR7. The high expression of receptors in CRC is often associated with a poor prognosis and aggressiveness of the tumor. The interaction of CXCL12 and its receptors activates signaling pathways that induce chemotaxis, proliferation, migration, and cell invasion. To this end, receptor inhibitors were developed, and their use in preclinical and clinical studies is ongoing. This review provides an overview of studies involving CXCR4 and CXCR7 in CRC with an update on their targeting in anti-cancer therapies.

Deep Learning Models for Poorly Differentiated Colorectal Adenocarcinoma Classification in Whole Slide Images Using Transfer Learning

Colorectal poorly differentiated adenocarcinoma (ADC) is known to have a poor prognosis as compared with well to moderately differentiated ADC. The frequency of poorly differentiated ADC is relatively low (usually less than 5% among colorectal carcinomas). Histopathological diagnosis based on endoscopic biopsy specimens is currently the most cost effective method to perform as part of colonoscopic screening in average risk patients, and it is an area that could benefit from AI-based tools to aid pathologists in their clinical workflows. In this study, we trained deep learning models to classify poorly differentiated colorectal ADC from Whole Slide Images (WSIs) using a simple transfer learning method. We evaluated the models on a combination of test sets obtained from five distinct sources, achieving receiver operating characteristic curve (ROC) area under the curves (AUCs) up to 0.95 on 1799 test cases.

Current Microsatellite Instability Testing in Management of Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer worldwide. In the past decade, mismatch repair deficiency (dMMR), manifested as microsatellite instability-high (MSI-H), has been recognized as a distinct mechanism promoting tumorigenesis in 15% of CRCs including 3% Lynch syndrome and 12% sporadic CRCs. As the molecular classifications of CRCs are continuously evolving, MSI-H CRCs appear to be the most homogeneous CRCs with distinct molecular, morphologic, and clinical features. MSI-H CRCs have dMMR causing MSI-H and genetic hypermutation but with diploid chromosomes. Morphologically, MSI-H CRCs appear as poorly differentiated or mucinous adenocarcinoma with characteristic lymphocytic infiltration. Most importantly, MSI-H CRCs have better stage-adjusted survival, do not respond well to standard 5-fluorouracil-based adjuvant chemotherapy, but do respond to immunotherapy. The United States Food and Drug Administration granted accelerated approval to immune checkpoint inhibitors, anti-programmed cell death protein-1 antibodies pembrolizumab and nivolumab, and the combination of nivolumab with anti-CTLA4 antibody ipilimumab for the second-line treatment of patients with stage IV MSI-H CRCs in 2017. There are still ongoing phase III clinical trials evaluating pembrolizumab and anti-programmed death-ligand 1 antibody atezolizumab as the first-line treatment in stage IV MSI-H CRCs and a phase I study on the combination of nivolumab and ipilimumab in patients with early stage CRC. These ongoing clinical studies on immunotherapy may lead to practice-changing results in the management of MSI-H CRCs. The National Comprehensive Cancer Network 2018 guidelines recommended MSI to be tested in all newly diagnosed CRCs. The MSI test will become increasingly vital in guiding adjuvant chemotherapy and immunotherapy in the management of CRCs.

Colon cancer stem cell markers CD44 and CD133 in patients with colorectal cancer and synchronous hepatic metastases

CD44 and CD133 mRNA expression as cancer stem cell markers in colorectal cancer were correlated with synchronous hepatic metastases and the clinicopathological factors, including patient survival. The CD44 and CD133 mRNA levels in 36 primary colorectal adenocarcinomas with synchronous hepatic metastasis were analyzed by reverse transcriptase polymerase chain reaction, with normalization relative to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Immunohistochemical analysis was performed on samples with typical mRNA expression patterns to investigate protein expression. Both CD44 and CD133 gene expressions were highest in hepatic metastasis tissue, followed by colorectal cancer and normal mucosa. The differences were statistically significant among groups of normal mucosa, colorectal cancer and hepatic metastasis tissue. CD44 mRNA expression was significantly associated with the tumor location (P=0.019) and histology (P=0.026). With a median follow-up period of 38 months, the 5-year disease-free survival rate of the patients with high CD44 mRNA expression in the CD44 hepatic metastasis tissue group was significantly lower than that of the patients with low expression (P=0.002). While the mRNA expressions in groups of CD44 colorectal tumor, CD133 colorectal tumor, and CD133 hepatic metastasis tissue were not significant. CD44 and CD133 mRNA were highly correlatively co-expressed in colorectal cancer with hepatic metastases. CD44 expression was an independent factor associated with patient survival, while CD133 did not show this pattern. Thus, CD44 is a more reliable marker for predicting hepatic metastases and survival. Larger prospective studies are required to confirm these findings.

Deficient HER3 expression in poorly-differentiated colorectal cancer cells enhances gefitinib sensitivity

Poorly-differentiated colorectal cancers (PD-CRC) show high metastatic potential and poor prognosis. However, molecular characteristics of PD-CRC remain unknown to date, particularly in molecular targeting therapy for patients with PD-CRC. In this study, we examined the expression of EGFR, HER2 and HER3 in PD-CRC by immunohistochemical analysis of archived clinical specimens of primary tumors and investigated the sensitivity of PD-CRC cell lines to gefitinib, a tyrosine kinase inhibitor for EGFR in vitro. We found that HER3 expression of PD-CRC among members of the HER family was significantly lower than that of well to moderately differentiated CRC (WMD-CRC) and 37% of the PD cases showed a EGFR+/HER2+/HER3- expression pattern. COLM-5 cells, a PD-CRC-derived cell line, which exhibits EGFR+/HER2+/HER3- expression pattern and recapitulates the typical histology of PD-CRC in xenografted tumors, showed high gefitinib sensitivity both in vitro and in vivo, compared with WMD-CRC cell line (COLM-2). Treatment with gefitinib resulted in the upregulation of p27Kip1 expression and induction of G1 cell cycle arrest, concomitantly associated with inactivation of PI3K/Akt signaling in COLM-5 cells and marked inhibition of xenografted tumors in nude mice, but not evident in COLM-2 cells. Treatment with sodium butyrate, an HDAC inhibitor that induces differentiation, upregulated the expression of HER3 associated with enhancement of the PI3K/Akt signaling, attenuated gefitinib-mediated p27Kip1 upregulation and reduced gefitinib sensitivity in COLM-5 cells in vitro. Furthermore, enforced expression of HER3 in COLM-5 cells resulted in significant resistance to gefitinib treatment both in vitro and in vivo. These findings suggest that deficient HER3 expression plays an important role in gefitinib sensitivity and that a malignant subset of PD with EGFR+/HER2+/HER3- phenotype is a potential candidate for a target of anti-EGFR molecular therapy such as gefitinib.

Relationships between p16 gene promoter methylation and clinicopathologic features of colorectal cancer: a meta-analysis of 27 cohort studies

Many existing studies have demonstrated that p16 promoter methylation might be correlated with the clinicopathologic features of colorectal cancer (CRC), but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationships between p16 promoter methylation and the clinicopathologic features of CRC. We searched the CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, and CBM databases from inception through August 1, 2013. Meta-analysis was performed using the STATA 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated under fixed- or random-effects models. Twenty-seven clinical cohort studies were included with a total of 3311 CRC patients. Our meta-analysis results revealed that p16 promoter methylation was associated with pathological characteristics of CRC (tumor, nodes, metastasis stage: OR=1.55, 95% CI: 1.14-2.13, p=0.006; lymph node metastasis: OR=2.40, 95% CI: 1.37-4.19, p=0.002; histologic grade: OR=2.72, 95% CI: 1.63-4.54, p<0.001; Dukes stage: OR=2.06, 95% CI: 1.57-2.71, p=0.002; tumor size: OR=1.99, 95% CI: 1.03-3.85, p=0.041; location: OR=2.49, 95% CI: 1.95-3.18, p<0.001, respectively). Subgroup analysis by ethnicity suggested that there were also significant correlations between p16 gene promoter methylation and pathological characteristics of CRC among both Caucasian and Asian populations (all p<0.05). Our meta-analysis suggests that promoter methylation of the p16 gene may be strongly correlated with the clinicopathologic features of CRC. Thus, p16 gene promoter methylation may be a potential biomarker for CRC.

Poorly differentiated colorectal cancers: correlation of microsatellite instability with clinicopathologic features and survival

OBJECTIVES

To evaluate the association of microsatellite instability (MSI) with clinicopathologic features and oncologic outcomes in patients with poorly differentiated colorectal cancer (PD).

METHODS

Study patients were divided into well-differentiated colorectal cancer (WD) and PD, which were compared according to histologic differentiation and MSI status.

RESULTS

Among 1,941 patients, PD was more frequent among microsatellite-unstable tumors (23.6%) than among microsatellite-stable (MSS) tumors (4.2%, P < .001). Patients with PD had worse 4-year overall survival rates than patients with WD (78.6% vs 88.2%, P = 0.010). Compared with MSS-PD tumors, MSI-PD tumors were characterized by right-colon predilection, larger size, and infrequent lymph node metastasis (P < .001 to P = .007).

CONCLUSIONS

The clinicopathologic characteristics of PD were closely associated with those of MSI. The outcomes of MSI-PD tumors were better than those of MSS-PD tumors, but this finding did not reach statistical significance.

Clinical significance of expression of hMLH-1 and hMSH-2 in sporadic colorectal carcinoma in Chinese Han patients in Xinjiang

AIM: To investigate the clinical significance of expression of hMLH-1 and hMSH-2 in sporadic colorectal carcinoma (SCC) in Chinese Han patients in Xinjiang.

METHODS: Expression of hMLH-1 and hMSH-2 was detected by immunohistochemistry in 95 cases of SCC specimens collected from Chinese Han patients in Xinjiang and 65 cases of normal colorectal mucosa (NCM) specimens.

RESULTS: The positive rates of hMLH-1 and hMSH-2 expression in NCM were both 100%. The negative rates of hMLH-1 (31.6%) and hMSH-2 (18.9%) expression were significantly higher in SCC than in NCM (both P < 0.05). The negative rates of hMLH-1 and hMSH-2 protein expression were significantly higher in right-sided tumors than in left-sided and rectal tumors (P = 0.006, 0.002), and in poorly differentiated tumors than in well differentiated tumors (P = 0.014, 0.008). There was a positive correlation between the expression of hMLH-1 and hMSH-2 proteins in SCC.

CONCLUSION: Loss of expression of hMLH-1 and hMSH-2 proteins in SCC was observed in some Chinese Han patients in Xinjiang. Loss of expression of hMLH-1 and hMSH-2 proteins correlates with tumor differentiation and location. Combined detection of hMLH-1 and hMSH-2 expression may be used for evaluating the severity and prognosis of colorectal cancer.

Location-related differences in sporadic microsatellite unstable colorectal cancer

BACKGROUND

Microsatellite unstable CRC is associated with female gender, large tumours, and poor differentiation. However, there are few reports about the characteristics and differences of sporadic microsatellite unstable CRC based on tumour location.

AIMS

Site-specific heterogeneity of sporadic microsatellite unstable colorectal cancer (CRC) based on location was elucidated.

METHODS

We enrolled 164 CRC patients with high-frequency microsatellite instability (MSI-H) from the prospective database of 2686 consecutive CRC patients who underwent surgical resection. We analysed microsatellite instability (MSI) and expression of mismatch repair (MMR) proteins (MLH1, MSH2, and MSH6).

RESULTS

Among the 164 MSI-H CRC, 105 (64.0%) were located in the proximal colon and 59 (36.0%) were located in the distal colon. The proximal MSI-H CRC was predominantly in female (p=0.014), had a more aggressive differentiation (p=0.001), was of advanced stage (p=0.035), and had a frequent loss of MLH1 expression (p=0.005) compared to the distal MSI-H CRC.

CONCLUSION

There were different clinicopathologic characteristics and MMR protein expression between proximal and distal MSI-H CRC. These findings suggest that the underlying carcinogenic pathway or molecular background differs according to location, despite being microsatellite unstable CRC.

Significant associations of mismatch repair gene polymorphisms with clinical outcome of pancreatic cancer

PURPOSE

DNA mismatch repair (MMR) is critical in maintaining genomic stability and may modulate the cellular response to gemcitabine. We hypothesized that genetic variations in MMR may affect the clinical outcome of patients with pancreatic cancer.

PATIENTS AND METHODS

We evaluated 15 single-nucleotide polymorphisms (SNPs) of eight MMR genes in 154 patients with potentially resectable pancreatic adenocarcinoma who were enrolled onto phase II clinical trials for preoperative gemcitabine-based chemoradiotherapy from 1999 to 2006. Associations of genotypes with tumor response to therapy (change of tumor size by radiologic evaluation at restaging), margin-negative tumor resection, and overall survival were evaluated using logistic regression and Cox proportional regression models.

RESULTS

Five, six, and 10 genotypes were significantly associated with tumor response to preoperative chemoradiotherapy, tumor resectability, and overall survival, respectively, in univariable analysis. TREX1 EX14-460C>T and TP73 Ex2+4G>A genotypes remained as significant predictors for tumor response, MLH1 IVS12-169C>T and TP73 remained as significant predictors for tumor resectability, and EXO1 R354H, TREX1, and TP73 remained as significant predictors for overall survival in multivariable models that included all clinical factors and genotypes examined. A strong combined genotype effect on each clinical end point was observed. For example, 20 of the 25 patients with zero to one adverse genotypes were alive, those with two, three, four, five, and six to seven adverse genotypes had median survival times of 36.2, 23.9, 16.3, 13.0, and 8.3 months, respectively (P < .001).

CONCLUSION

SNPs of MMR genes have a potential value as predictors for clinical response to chemoradiotherapy and as prognostic markers for tumor resectability and overall survival of patients with resectable pancreatic cancer.